8b – Factors affecting diffusion

Question 1

three factors

Answer 1

concentration, distance, surface area

Question 2

concentration

Answer 2

• The amount of a substance in a certain volume.
• The difference between 2 concentrations forms a concentration gradient; the greater the difference in concentration, the steeper the concentration gradient, so the faster the rate of diffusion.
• Rate of diffusion is directly proportional to concentration difference.

formula: c=m/v

Question 3

surface area

Answer 3

• Small particles can pass through membranes in organisms. If the surface area of a membrane is increased, there is more space through which particles can pass.
• This means more particles cross from one place to another in a certain time, so the overall rate of diffusion increases.

Question 4

distance

Answer 4

• The further the particles have to diffuse, the slower the rate of diffusion.
• So increasing the thickness of a membrane decreases rate of diffusion.
• Rate of diffusion is inversely proportional to the thickness of membrane (as one value increases, the other halves).

Question 5

fick’s law

Answer 5

rate of diffusion is directly proportional to (surface area) X (conc. difference)/ thickness of membrane